linux-kernel - Re: [PATCH bpf-next 1/3] uprobes: encapsulate preparation of uprobe args buffer

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Message-ID: <20240313151507.GA25452@redhat.com>
Date: Wed, 13 Mar 2024 16:15:08 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Andrii Nakryiko <andrii@...nel.org>
Cc: linux-trace-kernel@...r.kernel.org, rostedt@...dmis.org,
	mhiramat@...nel.org, bpf@...r.kernel.org,
	mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 1/3] uprobes: encapsulate preparation of uprobe
 args buffer

LGTM, one nit below.

On 03/12, Andrii Nakryiko wrote:
>
> +static struct uprobe_cpu_buffer *prepare_uprobe_buffer(struct trace_uprobe *tu,
> +						       struct pt_regs *regs)
> +{
> +	struct uprobe_cpu_buffer *ucb;
> +	int dsize, esize;
> +
> +	esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
> +	dsize = __get_data_size(&tu->tp, regs);
> +
> +	ucb = uprobe_buffer_get();
> +	ucb->dsize = dsize;
> +
> +	store_trace_args(ucb->buf, &tu->tp, regs, esize, dsize);
> +
> +	return ucb;
> +}

OK, but note that every user of ->dsize adds tp.size. So I think you can
simplify this code a bit more if you change prepare_uprobe_buffer() to do

	ucb->dsize = tu->tp.size + dsize;

and update the users.

Oleg.